1. Field of the Invention
This invention relates to a method for vaporizing nucleus pulposus within a lumbar disc of the vertebral column during a percutaneous diskectomy procedure using a laser.
2. Description of the Prior Art
Mechanically assisted percutaneous lumbar diskectomy of the prior art is used as a treatment of leg pain (sciatica) resulting from herniated discs of the lumbar vertebral column. The lumbar vertebral column consists of five vertebrae extending superiorly to the transitional thoracic vertebrae (1) at a first end and extending inferiorally to the sacrum (3) at a second end, as illustrated in FIG. 1. Between each lumbar vertebrae and between the lumbar and sacrum are cartilaginous discs. Each disc comprises an outer circular structure (annulus fibrosus) 2 which surrounds and tightly binds an inner gelatinous material (nucleus pulposus) 4 in the center, as illustrated in FIG. 2. The annulus fibrosus 2 is made up of concentric fibers which appear to cross each other obliquely. No blood vessels or nerves penetrate the nucleus.
Usually with age, the fibers of the annulus begin to degenerate. The degeneration results in the tearing of individual fibers when the vertebral column is stressed. Torn fibers can form fenestrations which allow the nucleus pulposus to move through the fibers of the annulus and bulge 5 outward away from the nucleus. If the bulged disc presses upon an adjacent nerve root 6, sciatica may develop, as illustrated in FIG. 3A.
It has been demonstrated that removing a portion of the nucleus with grasping forceps through a small cannula will produce good to excellent relief of pain in a majority of patients having symptoms indicative of sciatica. Once a portion of the nucleus is removed, the pressure against the nerve root causing the pain is relieved as the remaining nucleus contracts away from the pressure point, as illustrated in FIG. 3B. Hijikata S., Yamagishi M., Nakayama T., Oomori K., "Percutaneous Diskectomy: A New Treatment for Lumbar Disc Herniation", J. Toden Hospital 1975; 5:5-13. Since the Hijikata et al. article, mechanical forceps for microlumbar and percutaneous lumbar diskectomy procedures have been developed related to relieving sciatica pain.
U.S. Pat. No. 4,369,788, which issued in Jan. 25, 1983 to Goald teaches one such forceps device having an alligator jaw for microlumbar disc surgery. The forceps can be held by a surgeon in a reversed backhand grip which aids in their manipulation during microlumbar disc surgery procedures. For microlumbar disc surgery, a one-inch incision is made in the patient into which the forceps are inserted and the surgery is performed.
U.S. Pat. No. 4,545,374, which issued on Oct. 8, 1985 to Jacobson teaches a method and instruments for performing percutaneous diskectomy. The instrumentation taught by Jacobson is illustrated in FIGS. 4-10 and includes a speculum 20 which has a pair of semi-sharp edged blades 21 for piercing and stretching body tissue and pivotally hinged handles 22 for opening and closing the blades, as illustrated in FIG. 4. Speculum 20 has a guide means for guiding the speculum along a slender member such as a spinal needle (not shown) having a diameter of less than 3 millimeters. The guide means can be any form of a bore or hole through which the spinal needle can pass. Jacobson also teaches a cannula 30, which is illustrated in FIG. 5. Cannula 30 is a cylindrical tool having a bore 32 for passing instruments therethrough from outside the body to inside the body. Cannula 30 has an oval cross section for allowing different sized and shaped instruments therethrough. Cannula 30 also has anchor means for anchoring the cannula to the disc. Jacobson teaches using a trocar 40 which is inserted into cannula 30, as illustrated in FIGS. 6 and 7. Trocar 40 has a shaft 41 and a collar 42. Shaft 41 fits into hole 32 of cannula 30 to a point where collar 42 is located. Collar 42 is adjustable, thereby allowing shaft 41 to be adjustably inserted at different lengths into hole 32. Shaft 41 of trocar 40 is tapered at one end to a point 45 for anchoring into body tissue. A knife 50, as illustrated in FIG. 8, having a blade end 53, 54 and a handle 51 at an opposite end to the blade end is insertable through cannula 30. Blade end 53, 54 is curved to allow quick and more efficient fragmentation of disc nucleus pulposus because it undergoes a curved cutting path during use. Rongeur forceps 60 for removing fragmented disc nucleus material are inserted into the cannula after knife 50 is removed. Rongeur forceps 60 have scissor-like handles 61, 62 pivotally connected near one end by pivot 63 and a jaw 68, 69, wherein spreading the handles 61, 62 opens the jaw 68, 69 and squeezing the handles 61, 62 closes the jaw 68, 69, as illustrated in FIG. 9.
The percutaneous lumbar diskectomy procedure taught by Jacobson includes placing a patient in a lateral decubitus position on an operating table; anesthetizing the patient usually with a long spinal needle which is guided into the disc area with the aid of fluoroscopic x-ray; incising a 1 centimeter long skin incision to create a percutaneous channel 9 with a speculum 20, as illustrated in FIG. 10. Speculum 20 is constructed to open and close and has jaw blades with semi sharp edges which spread rather than cut body tissue. Guiding speculum 20 by guide means over spinal needle 24 until properly located; spreading the jaws of speculum 20 open to create channel 9 for the insertion of cannula 30 to act as a conduit for the insertion of tools; inserting cannula 30 with the aid of a trocar 40 and removing speculum 20. Trocar 40 adds stiffness to the flexible cannula and eases its insertion along with the guidance of fluoroscopic x-ray. Trocar 40 can have pointed tip 45 which sticks into the disc capsule 8 and prevents lateral movement of cannula 30. Passing a nerve stimulator 80 (not shown) down channel 9 with cannula 30 or trocar 40. Stimulator 80 will cause motion in one of the patient's legs if it makes nerve contact, thereby signaling the surgeon that a slightly different insertion position is necessary. Cutting a hole in the annulus fibrosus surrounding the nucleus with knife 50 or another trocar having a rotatable reamer; fragmenting the nucleus pulposus with knife 50, ultrasonics, laser or dissolving chemicals; removing fragments of nucleus pulposus with Rongeur forceps 60 and/or suction. Rongeur forceps 60 preferably have large angles jaws which sweep a wide arc and several Rongeur forceps may be used each with slightly different angled jaws to remove nucleus pulposus from different portions of the disc. The surgeon uses rotational motion about an axis defined by the shaft of the forceps in order to scoop out material about an axis of revolution. A Z-head Rongeur forceps can create a cavity of revolution by removing a large amount of nucleus material upon rotation. Flushing the cavity created in the nucleus pulposus with saline solution to clean out the space; suctioning out the solution and any debris contained therein; removing the cannula and stitching up the fat and fascia underneath the skin; and bandaging the outer skin surface with an adhesive strip to prevent suture scars.
Jacobson taught that this procedure requires one to two days recovery time, that outpatient convalescence is possible and that the total procedure time is approximately 15 minutes. Nevertheless, the instrumentation and procedure require extensive manipulation of tools by the surgeon, that a more streamlined procedure using fewer tools would be desirable. In practice, the Jacobson procedure has a 60% failure rate in relieving back pain and takes greater than 15 minutes to perform.
U.S. Pat. No. 4,678,459 issued to Onik et al. on July 7, 1987 teaches using an irrigating, cutting and aspirating system for percutaneous surgery. Onik et al. teaches using a system for removing nucleus pulposus tissue 79 which includes a probe and a guillotine type of cutting means 78 for cutting the nucleus pulposus 79, as illustrated in FIG. 11. The severed or cut fragments of nucleus pulposus 79 are removed from the cutting means 78 using an internal fluid irrigation system and a vacuum to aspirate the severed fragments out of the disc area, through the system, and out of the patient. This system provides for a relatively fast diskectomy procedure compared to the other prior art because nucleus pulposus can be fragmented and removed without the need to manipulate many small blades, knives and forceps, as described for the Jacobson U.S. Pat. No. 4,545,374. The probe and guillotine-type cutting means taught by Onik et al. is sold on the market as a Nucleotome Probe 70, as illustrated in FIG. 15. This instrument is the most widely used instrument for percutaneous diskectomy. The procedure and instrumentation used to implement the Nucleotome Probe 70 include placement of a FlexTrocar 71 into a 3 millimeter skin incision made on the side of the patient's body where the herniation is evident. The FlexTrocar 71 is inserted until it contacts the annulus fibrosus 72 of the herniated disc, as illustrated in FIG. 12, using the guidance of a fluoroscopic X-ray. Once the FlexTrocar 71 is in place, a straight cannula 73 having a tapered dilator 74 is passed over the FlexTrocar 71 and inserted down to the annulus 72 wall, as illustrated in FIG. 13. The position of the straight cannula 73 is confirmed fluoroscopically. Once the cannula 73 is in place, the tapered dilator 74 is removed from the cannula 73. A trephine 75 is inserted through the cannula 73 and over the FlexTrocar 71. The trephine 75 is rotated in a clockwise motion with slight pressure to incise the annulus, as illustrated in FIG. 14. The trephine 75 and the FlexTrocar 71 are subsequently removed from the patient's body. The Nucleotome Probe 70 is inserted into the cannula 73 after the trephine 75 and FlexTrocar 71 are removed. The Nucleotome Probe 70 locks into place on the cannula 73, as illustrated in FIG. 15. When the Nucleotome Probe 70 is activated, the nucleus pulposus is cut into fragments which are removed with irrigation fluids and suction, all within the Nucleotome Probe 70. The Nucleotome Probe 70 is activated until no further material can be extracted. Once complete, the Nucleotome Probe 70 and cannula 73 are removed and the entry point is covered with a sterile bandage. The cutting and extracting process alone using the Nucleotome Probe 70 normally takes between 20 to 30 minutes.
In 1989, P. W. Ascher, D. S. Choy and H. Yuri suggested using lasers to vaporize disc material in a percutaneous diskectomy procedure. Ascher et al. believed the CO.sub.2 laser was not a viable choice for percutaneous diskectomy because an optical fiber for the CO.sub.2 laser was not yet available. Ascher et al. reported using an Nd:YAG laser at 1060 nm since an optical fiber was available. Ascher et al. were aware that the Nd:YAG laser at 1060 nm had low adsorption in water and white tissue and high absorptivity in water and white tissue is necessary to produce effective vaporization of nucleus pulposus. Tests were performed with less than encouraging results. Also, Ascher et al. reported using a Nd:YAG laser at 1320 nm and claimed it produced twice as much volume reduction as compared to the 1060 nm laser. Nevertheless, Ascher et al. reported that only the CO.sub.2 laser or the Er:YAG laser would produce sufficient results in about 10-15% of patients having the requisite symptoms. Abstract No. 202, p. 48, entitled "Percutaneous Nucleus Purposes Denaturization and Vaporization of Protruded Discs", American Society for Laser Medicine and Surgery: Lasers in Surgery and Medicine, Supplement 1, 1989.
The results of the Ascher et al. investigations did not produce safe and effective results using a laser to vaporize nucleus pulposus from herniated discs. It would be desirable if a laser technique and laser instrumentation were available to perform percutaneous diskectomies so that nucleus pulposus from herniated discs could be vaporized using a laser in a safe and effective way which is faster than cutting and irrigating using the Nucleotome Probe and which would eliminate the need to cut and remove fragmented debris from the patient.